Abstract: Due to the fact that oil based drilling fluid liquid emulsifiers possess high viscosity and poor mobility, and the common solid emulsifiers have poor emulsification effect and complicated preparation procedure, a solid emulsifier EmuL-S with strong emulsifying ability in oil based drilling fluid has been developed by simple amidation reaction. Its structure was analyzed by using an infrared spectrum, and the emulsifying properties were investigated by means of electrical stability, emulsification rate, the amount of liquid dropout and optical microscopy. The performance of oil based drilling fluid containing the new emulsifier was evaluated. The results showed that the solid emulsifier EmuL-S contains the required group in the design. When the oil-water ratio is 80:20, with a solid emulsifier EmuL-S dosage of 3.3%, the water-in-oil emulsion has a breaking voltage of greater than 1000 V, the emulsion rate is greater than 90%, the amount of liquid dropout is less than 0.7mL, and the temperature is resistant to 180℃. The oil based drilling fluids with EmuL-S has a density up to 2.0 kg/L, temperature resistance is up to 180℃, with high sedimentation stability, excellent rheological properties, ratio of YP/PV is higher than 0.21, and the breaking voltage is greater than 800 V. Its pollution resistance capacities are at 15% water, 15% inferior soil, 9% cuttings and 9% CaCl2. Studies showed that the solid emulsifier EmuL-S has excellent emulsifying ability and high temperature resistance capability, and has the advantages of easy preparation and mass production, which can address the problems that exist in conventional emulsifiers.